JP2007318257A - Information embedding device, information restoring device, information embedding method, information restoring method, control program, computer-readable recording medium recording the same, and printed matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information embedding device and an information restoring device which can positively prevent unauthorized extraction of information added to printed matter and control method of these, a control program, a computer-readable recording medium recording the same, and printed matter. <P>SOLUTION: The information embedding device is provided with: a feature acquiring section 13 for extracting physical feature of printed matter; a key generating section 14 for generating a key associated with the printed matter on the basis of the physical feature of the printed matter extracted by the feature acquiring section 13; an encrypting section 15 for encrypting information to be embedded in the printed matter by using the key generated by the key generating section 14; and an information embedding section 16 for embedding the information encrypted by the encrypting section 15 into the printed matter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information embedding device for embedding watermark information in a printed material, an information embedding device for embedding information encrypted with a key generated based on a physical characteristic of the printed material, an information embedding method, an image processing program, and an image processing program. The present invention relates to a machine-readable recording medium and printed matter.

  In recent years, a method has been proposed in which content information is acquired via a printed material by giving additional information to the printed material. Specifically, for example, as disclosed in Patent Document 1, additional information such as audio data is printed and recorded on a printed matter in which a readable image such as a document or a photograph is recorded. Thus, the voice can be heard while viewing the readable image by reading the voice image with the dedicated reading device.

  Patent Document 2 describes a method of adding not only audio data but also so-called multimedia information including image and video data, text data, etc. to a printed matter in an optically readable form. . Specifically, the read information can be reproduced by printing and recording an optically readable dot code on a recording medium such as paper or a sticker. The dot code is used and reproduced by a dot code decoding control file including at least one of a control program and parameters for controlling an application program operating on the PC and an application program operating on the PC. Application data files such as audio files.

  Thus, various information can be added to a recording medium such as a printed matter.

  By the way, in recent years, illegal copying, forgery, falsification, etc. of printed matter to which additional information is given have become a major social problem. In particular, with the development of digital image forming apparatuses such as printers and copiers, these illegal acts are easily performed. For example, by copying a sheet on which a dot code including multimedia information described in Patent Document 2 is printed, the multimedia information can be easily duplicated. Thus, copyright is infringed by illegally copying information.

  Therefore, an example of a method that can prevent or suppress the extraction of information due to the above fraud is disclosed in Patent Document 3.

  Patent Document 3 discloses an example of a system that can easily determine whether it is an original or an unauthorized copy. The system is configured to guarantee the original of a printed matter (printed paper) by discriminating between deterioration that has occurred during printing of the original and deterioration that has occurred due to subsequent copying. Specifically, at the time of printing, the remaining watermark amount is detected from the print pattern of the printed material, converted into generation management information, and printed on the printed material in advance. At the time of authentication, watermark information and generation management information are detected from the print pattern of the read printed matter, the watermark is verified from the watermark information, and the remaining watermark amount is calculated. Then, the remaining watermark amount is extracted from the generation management information, and the original guarantee is confirmed by comparing the remaining watermark amount calculated by the verification of the watermark with the remaining watermark amount extracted from the generation management information.

As a result, it is possible to determine whether or not it is an original, so that it is possible to prevent information from being taken out due to the above-mentioned fraudulent acts.
JP 10-51645 A (published February 20, 1998) JP 2001-222433 A (released on August 17, 2001) JP 2002-344736 A (published on November 29, 2002)

  However, in the configuration of Patent Document 3, the degree of deterioration is reduced due to the development of printers and copiers, so that there is a high possibility that confirmation of originality cannot be confirmed in the future by comparing the remaining watermarks. . As a result, there is a risk that an illegal copy, which is fake as the original, is used and information is taken out. As described above, the conventional technology cannot reliably prevent the information added to the printed matter from being taken out by an illegal act.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an information embedding device, an information restoration device, and a control thereof that can reliably prevent unauthorized extraction of information added to printed matter. A method, a control program, a computer-readable recording medium on which the program is recorded, and a printed matter.

  In order to solve the above problems, the information embedding device of the present invention is an information embedding device for embedding information in a printed material, a feature acquisition unit that extracts physical characteristics of the printed material, and the printed material that is extracted by the feature acquisition unit. A key generation unit that generates a key associated with the printed material based on the physical characteristics of the key, and an encryption unit that encrypts information to be embedded in the printed material using the key generated by the key generation unit; An information embedding unit for embedding the information encrypted by the encryption unit in the printed matter is provided.

  In order to solve the above-described problem, the information embedding method of the present invention is an information embedding method for embedding information in a printed material. The information acquiring method extracts a physical feature of the printed material and the feature acquiring step extracts the physical feature. Based on the physical characteristics of the printed material, a key generating step for generating a key associated with the printed material, and encryption for encrypting information embedded in the printed material using the key generated by the key generating step And an information embedding step of embedding the information encrypted by the encryption step in the printed matter.

  Here, the physical characteristics of the printed material include characteristics unique to the printed material, such as paper fiber pattern, paper surface irregularities, paper material, density and transparency due to overlapping of paper fibers, and density depending on the color of paper fibers. Say.

  According to said structure, the information embedded in this printed matter is encrypted using the key produced | generated based on the physical characteristic which printed matter has. Then, the encrypted information is embedded in the printed material.

  As described above, since the key is generated based on the characteristic unique to the printed material, a different key is generated for each printed material. In addition, the information is embedded in the printed material using a key generated based on the unique characteristics of the printed material. Therefore, in order to extract information embedded in the printed material, it is necessary to use the same key as the generated key.

  Here, for example, consider a case where a printed matter in which information is embedded, that is, a copy of an original is to be obtained illegally. First, since the information is encrypted using a key generated based on the characteristics unique to the printed material (original) and embedded in the printed material, the information cannot be extracted simply by copying. Therefore, in order to extract the information from the duplicate, it is necessary to use the same key as the key generated based on the characteristic unique to the printed matter (original) as described above. However, since the physical characteristics of the printed material (original) and the copied material are different from each other, the keys generated from them are different from each other. Therefore, it is impossible to extract the information from the duplicate.

  As described above, in the above-described configuration, since the characteristic unique to the printed material is used, the information embedded in the printed material can be extracted only from the printed material (original). Accordingly, it is possible to prevent information from being taken out illegally, for example, by illegally copying a printed matter including the information. Therefore, it is possible to protect the copyright of the information included in the printed material. It is also possible to easily determine whether or not the original.

  In addition, as a method of embedding information in a printed matter, there is a digital watermark method, a method by changing a pixel value of an image printed on the printed matter, a method by changing a frequency component of an image printed on the printed matter, and a method for printing on the printed matter. A method by changing the dots that make up the character font that makes up the image, a method by changing the position of the characters that make up the image, a method by drawing a pattern assigned by the code that makes up the information on the background of the image, etc. There is.

  Examples of encryption methods using keys include stream ciphers (RC4 and the like), common key cipher block ciphers (DES, AES, and the like), public key ciphers (RSA and the like), and the like.

  The information embedding device according to the present invention further comprises encoding means for performing error correction encoding on the information embedded in the printed matter in the information embedding device described above, and the encryption means uses the error correction code by the encoding means. It is preferable to encrypt the encrypted information.

  According to the above configuration, the information to be embedded in the printed matter is encrypted after error correction coding. As a result, even when an error occurs when extracting the information embedded in the printed matter, the error can be corrected, so that the information can be accurately extracted.

  Examples of error correction coding methods include CRC (Cyclic Redundancy Checking) coding, BCH (Bose, Chaudhuri, Hocquenghem) coding, RS (Reed Solomon) coding, and the like.

  In the information embedding device according to the present invention, in the information embedding device described above, it is preferable that the printed material is paper, and the physical feature of the printed material is a fiber pattern of the paper.

  According to said structure, the physical characteristic which the said printed matter has is the fiber pattern of paper. The fiber pattern of the paper is a characteristic unique to the printed matter, and can be recognized by, for example, a scanner. As a result, a different key can be accurately generated for each printed material, so that the same key as the key generated from the printed material is not erroneously generated from the duplicate. Therefore, it is possible to reliably prevent information from being taken out by illegal copying or the like.

  In the information embedding device according to the present invention, in the information embedding device described above, it is preferable that the information embedding unit embeds the information in a printed matter by a digital watermark technique.

  According to the above configuration, the information embedded in the printed material is watermark information. As a result, it is impossible to visually recognize that information is embedded in the printed matter. In addition, it is possible to prevent deterioration of embedded information.

  In the information embedding device according to the present invention, it is preferable that in the information embedding device described above, the information embedding unit repeatedly performs the process of embedding the watermark information at an arbitrary position of the printed matter.

  According to said structure, the process which embeds the said watermark information in the arbitrary positions of the said printed matter is performed repeatedly. Thereby, it is possible to reduce the possibility of an error when taking out the information embedded in the printed matter.

  In the information embedding device according to the present invention, in the information embedding device described above, it is preferable that the information embedding unit repeatedly performs the process of embedding the information in part or the entire surface of the printed matter.

  According to said structure, the process which embeds the said information in the one part or the whole surface of the said printed matter is performed repeatedly. Thereby, the possibility that an error may occur when the information embedded in the printed material is taken out can be further reduced.

  The information embedding device of the present invention further comprises image coding means for image-coding the information encrypted by the encryption means in the information embedding device described above, wherein the information embedding means includes the image code It is preferable to add the image code generated by the converting means to the printed matter.

  Here, the image code refers to an image code such as a one-dimensional code such as a barcode or a two-dimensional code such as a QR code.

  According to the above configuration, the generated image code is added to the printed matter. Thereby, the reading accuracy and the processing speed can be improved as compared with the digital watermark method.

  In the information embedding device according to the present invention, in the information embedding device described above, the image encoding unit performs error correction encoding on the information encrypted by the encryption unit a plurality of times to generate an image code. Is preferred.

  According to the above configuration, the information encrypted by the encryption unit is repeatedly subjected to error correction coding a plurality of times to be image coded. As a result, even when an error occurs when an image code that has been converted into an image code is read, the error can be corrected, so that information can be accurately extracted.

  In order to solve the above problems, the information restoration apparatus of the present invention is an information restoration apparatus that restores information embedded in a printed matter, the feature acquisition unit that extracts the physical characteristics of the printed matter, and the features described above. Based on the physical characteristics of the printed matter taken out by the obtaining means, the key generation means for generating a key associated with the printed matter and the key generated based on the physical characteristics of the printed matter are encrypted. An information acquisition unit that extracts information embedded in the printed material; and a decryption unit that decrypts the information extracted by the information acquisition unit using the key generated by the key generation unit. It is a feature.

  In addition, the information restoration method of the present invention is an information restoration method for restoring information embedded in a printed material in order to solve the above-mentioned problem, a feature acquisition step for extracting physical characteristics of the printed material, and the above features Based on the physical characteristics of the printed material taken out in the obtaining step, a key generation step for generating a key associated with the printed material, and the key generated based on the physical characteristics of the printed material is encrypted. And an information acquisition step for extracting information embedded in the printed material, and a decryption step for decrypting the information extracted by the information acquisition step using the key generated by the key generation step. Yes.

  Here, the physical characteristics of the printed material include characteristics unique to the printed material, such as paper fiber pattern, paper surface irregularities, paper material, density and transparency due to overlapping of paper fibers, and density depending on the color of paper fibers. Say.

  According to said structure, the information encrypted using the key produced | generated based on the physical characteristic which printed matter has is decoded using the key produced | generated based on the physical feature which printed matter has.

  Here, for example, consider a case where the information is extracted from a printed material in which the information is embedded. In this case, since the printed matter from which the information is extracted is a printed matter (original) including the information, the physical characteristics to be taken out are equal. For this reason, the keys generated based on the physical characteristics are also the same. Information can be decrypted by using the same key as that used for encryption. Thereby, information can be extracted from the image.

  On the other hand, when an attempt is made to illegally obtain information by copying a printed material (original) in which information is embedded, the physical properties of the printed material (original) and the duplicate are different from each other. The keys are different from each other. Therefore, it is impossible to extract the information from the duplicate.

  As described above, in the above configuration, since the characteristic unique to the printed material is used, when the printed material includes information, that is, it is an original, information can be extracted from the printed material. In addition, it is possible to prevent information from being illegally taken out by illegally copying a printed material including information. Therefore, it is possible to protect the copyright of the information included in the printed material. Furthermore, it is possible to easily determine whether or not the original.

  Note that the decryption method using a key is the same as the encryption method. For example, a stream cipher (RC4 or the like), a common key cipher block cipher (DES, AES, or the like), or a public key cipher (RSA or the like). ) And the like.

  In the information restoration apparatus according to the present invention, it is preferable that in the information restoration apparatus described above, the printed material is paper, and the physical characteristic of the printed material is a fiber pattern of the paper.

  According to said structure, the physical characteristic which the said printed matter has is the fiber pattern of paper. The fiber pattern of the paper is a characteristic unique to the printed matter, and can be recognized by, for example, a scanner. As a result, a different key can be accurately generated for each printed material, so that the same key as the key generated from the printed material is not erroneously generated from the duplicate. Therefore, when the printed material is a printed material (original) including information, the information can be reliably extracted. Further, it is possible to reliably prevent information from being taken out by illegal copying or the like.

  The information embedding device and the information restoring device may be realized by a computer. In this case, the information embedding device and the information restoring device are realized by a computer by operating the computer as each of the means. A control program for each device to be executed and a computer-readable recording medium on which the control program is recorded also fall within the scope of the present invention.

  As described above, the information embedding device according to the present invention includes a key generation unit that generates a key associated with the printed material based on the physical characteristics of the printed material extracted by the feature acquisition unit, and the key generation unit. And encryption means for encrypting the information to be embedded in the printed matter using the key generated by the above.

  Further, as described above, the information embedding method of the present invention includes a key generation step for generating a key associated with the printed material based on the physical characteristics of the printed material extracted by the feature acquisition step, and the key And an encryption step of encrypting information to be embedded in the printed matter using the key generated in the generation step.

  Thereby, the information embedded in the printed material can be extracted only from the printed material (original) on which the image is printed. Therefore, it is possible to reliably prevent unauthorized extraction of information added to the printed material.

  An embodiment of the present invention will be described below with reference to the drawings. In the following description, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[Embodiment 1]
FIG. 1 is a block diagram showing a schematic configuration of a computer that functions as an information embedding device and an information restoration device according to the present embodiment. Here, before describing the information embedding device and the information restoring device, an outline of the computer 100 will be briefly described below.

  As shown in FIG. 1, a computer 100 has a display device 103 composed of a liquid crystal or a CRT (cathode ray tube) or the like for displaying information, and inputs information such as various instructions and characters by key operation from the outside. A data input unit 105, a CPU 102 for centrally controlling the computer 100, a memory 106 including a ROM or a RAM, a fixed disk 107, and an FD (Flexible Disk) 108 are detachably provided. Yes. The computer 100 also includes an FD drive device 109 that can access the FD 108 and a CD-ROM (Compact Disc Read Only Memory) 110 that can be freely attached and detached, and a CD-ROM drive device 111 that can access the CD-ROM 110, A communication I / F 112 and a printing unit 101 are further provided.

  The communication I / F 112 has a function of connecting the communication path 113 and the computer 100 in a communicable manner. Therefore, the computer 100 can perform data communication with the printer 1 (not shown) via the communication path 113. Various networks including the Internet can be applied to the communication path 113. In the computer 100, data processed by the CPU 102 for printing is sent to the printing unit 101, where it is printed on paper and output. Note that it may be transmitted to the printer 1 (not shown) via the communication I / F 112 and the communication path 113, and printed and output by the printer 1.

  Note that the computer 100 of FIG. 1 may be provided with a magnetic tape device in which a cassette type magnetic tape is detachably mounted to access the magnetic tape.

  Software installed in the computer 100 is stored and distributed in a recording medium such as the CD-ROM 110 and the FD 108, and the CPU 102 passes the CD-ROM drive device 111 or the FD drive device 109 to a predetermined recording area of the computer 100 or workstation. Read and execute.

  The computer 100 including the above components functions as an information embedding device and an information restoration device according to the present embodiment. Hereinafter, the information embedding device and the information restoring device will be described in detail.

(About information embedding device)
FIG. 2 is a block diagram showing a schematic configuration of the information embedding device and the information restoring device according to the present embodiment.

The information embedding device 10 is a device that embeds embedded information in a recording medium (printed material) such as paper and outputs (prints) it together with a document image. The information embedding device 10 includes an information reading unit 11, an encoding unit 12, a feature acquisition unit (feature acquisition unit) 13, a key generation unit (key generation unit) 14, and an encryption unit (encryption unit) 15. , An information embedding unit (information embedding means) 16 and an output unit 17 are provided.

  The image is data created by a document creation tool, an image creation tool, or the like, and the embedding information is embedded in a recording medium such as paper in a format other than characters or characters, for example, character strings, images, audio Etc. In the present embodiment, for convenience of explanation, the image is described as “document image”, the embedded information is described as “confidential information”, and the image in which the confidential information is embedded is described as “embedded document image”. The embedded information may be directly embedded in a recording medium such as paper, or may be embedded in the document image printed on the recording medium. Hereinafter, a description will be given by taking as an example the case where the above-described embedding information is embedded in a document image.

  The information reading unit 11 reads a document image and confidential information created by the data input unit 105 and stored in the memory 106 or the fixed disk 107. The document image may be any of color, gray scale, and binary.

  The encoding unit 12 performs error correction encoding on the confidential information read by the information reading unit 11. The error correction coding uses existing techniques such as CRC (Cyclic Redundancy Checking) coding, BCH (Bose, Chaudhuri, Hocquenghem) coding, and RS (Reed Solomon) coding.

  The feature acquisition unit 13 extracts physical features from an image captured by the scanner 104 and stored in the memory 106 or the fixed disk 107. The scanner 104 captures a document image printed on paper as a color, gray scale, or binary image, and may be either a reflection type or a transmission type. The feature acquisition unit 13 takes out physical features of the paper, specifically, a fiber pattern. The physical characteristics of the paper are not limited to the fiber pattern, but include, for example, irregularities on the paper surface, paper material, density and transparency due to overlap of paper fibers, and density due to the color of the paper fibers. May be. Further, the fiber pattern of the paper is taken out from an arbitrary position and an arbitrary range of the paper. Further, the position and range to be extracted may be embedded as a digital watermark. The extracted fiber pattern of the paper is stored in the memory 106 or the fixed disk 107 using an existing image storage method such as bitmap or JPEG (Joint Photographic Experts Groups).

  The key generation unit 14 generates a key stream (key) based on the fiber pattern of the paper taken out by the feature acquisition unit 13. A specific method for generating the key stream will be described later.

  The encryption unit 15 encrypts the confidential information that has been error correction encoded by the encoding unit 12 with the key stream generated by the key generation unit 14. A specific method for encrypting confidential information with a key stream will be described later.

  The information embedding unit 16 embeds confidential information encrypted by the encryption unit 15 in a document image. A specific method for embedding the confidential information in the document image will be described later.

  The output unit 17 is an output device including the print unit 101, and prints a document image in which confidential information is embedded by the information embedding unit 16 on a recording medium such as paper. Note that the output unit 17 may transmit the output data to the printer 1 (not shown) via the communication I / F 112 and the communication path 113 so that the printer 1 prints and outputs the data.

  Next, an operation of embedding information in the information embedding device 10 will be described. FIG. 3 is a processing flowchart showing an operation example of the information embedding device 10. It is assumed that the document image and confidential information are stored in advance in the memory 106, the fixed disk 107, and the like.

  First, in step (hereinafter, step is abbreviated as S) 10, the document image and confidential information stored in the memory 106 or the fixed disk 107 are read out by the information reading unit 11, and the paper fiber is read by the feature acquisition unit 13. The pattern is taken out.

  Subsequently, the key generation unit 14 codes the fiber pattern of the paper taken out by the feature acquisition unit 13 to generate a key stream (S11). Next, the encoding unit 12 performs error correction encoding on the confidential information read by the information reading unit 11 (S12). Next, the encryption unit 15 encrypts the confidential information that has been error correction encoded by the encoding unit 12 with the key stream generated by the key generation unit 14 (S13). Then, the confidential information encrypted by the encryption unit 15 is embedded in the document image by the information embedding unit 16 (S14).

  Note that the document image in which the confidential information is embedded is printed and output by the output unit 17.

  Here, a specific method of generating a key stream by encoding a fiber pattern will be described with reference to FIG.

  A basic method of generating a key stream from the fiber pattern extracted by the feature acquisition unit 13 is performed according to the following procedure.

  First, pre-processing is performed on a paper fiber pattern. In the preprocessing, for example, density conversion processing such as non-linear density conversion is performed so that there is no difference in the result of the fiber pattern obtained by the accuracy of the scanner 104. Since the fiber pattern is a light and dark pattern due to overlapping of fibers, the light and dark pattern is For sharpening, sharpening filter processing and the like can be mentioned.

  Next, feature amounts are extracted from the preprocessed image. As a feature amount extraction method, for example, an n × n sample of an image is taken, and the density value at the sample point is used as the feature amount. Note that not only the density value but also the value of the average gradient of density change around the sample point may be used. Further, a threshold value for density may be obtained, and the position and area of a pixel group having a density value equal to or lower than the threshold value and the value of the distance between the pixel groups may be used as the feature amount. Furthermore, the image may be subjected to frequency conversion by DFT (Discrete Fourier Transform), FFT (Fast Fourier Transform), DCT (Discrete Cosine Transform), wavelet transform, etc., and the feature quantity may be acquired from the frequency band.

  Next, the extracted feature quantity is coded. As for coding, there is a method of generating by a simple arrangement of sample point values.

  Finally, the coded code is used as a key stream. When the code is used as the key stream, the code stream may be repeated several times. The pre-processing and the feature amount acquisition method are not limited to the above-described methods. Further, the bit size at the time of encoding is not limited.

  Here, a specific process for encrypting the error correction encoded confidential information with the key stream will be described with reference to FIG.

  First, the confidential information read from the memory 106 or the fixed disk 107 is encoded by the information reading unit 11 and the error correction encoding is performed by the encoding unit 12. Then, the encryption unit 15 encrypts the confidential information subjected to error correction coding using the key stream generated by the key generation unit 14. As a result, encrypted confidential information is obtained.

  In the present embodiment, it is preferable to use a stream cipher (RC4 or the like) as an encryption method using a key. The key generated by the key generation unit 14 configures the fiber information according to the performance of the scanner and the surrounding environment even when the fiber information of the same paper is acquired when the fiber information is read from an optical device such as a scanner. Since there is a low possibility that the bit string to be unique is an error, an error may occur. In this regard, stream ciphers have a basic structure in which XOR (exclusive or) processing is performed for each bit (byte) of the equality and the key. In this case, the ciphertext is erroneous only at the wrong part corresponding to the key. When decryption is performed, there is a high possibility of error correction using an error correction code before encryption.

  In consideration of the case where no error occurs, the encryption method using a key may use not only the above-mentioned stream cipher but also a block cipher of a common key cipher (DES, AES, etc.) and a public key cipher (RSA, etc.). Is possible.

  Here, a specific process for embedding confidential information encrypted by the encryption unit 15 in a document image will be described with reference to FIG.

  In the present embodiment, encrypted confidential information is embedded in a document image using a digital watermark technique. Note that the embedding method is not limited to the digital watermark method. For example, the method by changing the dots constituting the character font constituting the document image, the method by changing the position of the characters constituting the document image, or An existing embedding technique such as a method by drawing a pattern assigned by a code constituting information on the background of a document image can be used. In addition, since there is a possibility that an error occurs when the confidential information is extracted, a method of repeatedly embedding the confidential information in the document image is also conceivable.

  With the above processing, confidential information can be embedded in the document image.

(About information restoration device)
The information restoration device 20 is a device that takes in a document printed on a paper medium as an image and restores the information embedded by the information embedding device 10. As shown in FIG. 2, the information restoration apparatus 20 includes an input unit 21, a feature acquisition unit (feature acquisition unit) 22, a key generation unit (key generation unit) 23, an information acquisition unit (information acquisition unit) 24, and a decryption unit. Section (decoding means) 25 and error correction section 26. The paper medium is printed by the information embedding device 10, and confidential information is embedded in the document image printed on the paper medium by the digital watermark method. In the following description, the document image is represented as a digital watermark embedded document image.

  The feature acquisition unit 22 extracts a physical feature from a digital watermark embedded document image that is captured by the input unit 21 such as the scanner 104 and stored in the memory 106 or the fixed disk 107. The scanner 104 captures a document image printed on paper as a color, gray scale, or binary image, and may be either a reflection type or a transmission type. The physical feature taken out by the feature acquisition unit 22 is the same as the physical feature taken out by the feature acquisition unit 13 of the information embedding device 10, and in this embodiment is a paper fiber pattern.

  Further, the position and range where the feature acquisition unit 22 takes out the fiber pattern of the paper are the same as the position and range where the feature acquisition unit 13 of the information embedding device 10 takes out. Here, as a configuration in which the feature acquisition unit 22 of the information restoration device 20 and the feature acquisition unit 13 of the information embedding device 10 extract the fiber pattern at the same position and range on the paper, the feature acquisition unit 13 extracts the fiber pattern. And a method of embedding a range as a digital watermark in a document image and determining a position and a range where the feature acquisition unit 22 takes out the fiber pattern based on the embedded information. Further, the information restoration device 20 and the information embedding device 10 share the same feature acquisition unit, and information (paper fiber pattern) extracted by the information embedding device 10 stored in the feature acquisition unit is used as the information restoration device. 20 may be configured to read from the feature acquisition unit.

  The key generation unit 23 generates a key stream based on the paper fiber pattern extracted by the feature acquisition unit 22. The method for generating the key stream is the same as the method performed by the key generation unit 14 in the information embedding device 10 described above. The information restoring device 20 and the information embedding device 10 may share the same key generation unit.

  The information acquisition unit 24 extracts confidential information from the digital watermark embedded document image. A specific method for extracting confidential information from a digital watermark embedded document image will be described later.

  The decryption unit 25 decrypts the confidential information extracted by the information acquisition unit 24 using the key stream generated by the key generation unit 23. Note that the decryption using the key stream can be realized by performing confidential information and XOR (exclusive or) processing by the stream cipher (RC4 or the like) method as in the above-described encryption method. Further, as other methods of decryption using a key, for example, block ciphers of common key ciphers (DES, AES, etc.), public key ciphers (RSA, etc.) and the like can be cited, as with the above-described encryption method. .

  The error correction unit 26 performs error correction when the confidential information decrypted by the decryption unit 25 has an error. Note that the error correction method uses an existing technology corresponding to the error correction coding of the information embedding device 10.

  Next, an operation of restoring the digital watermark embedded document image in the information restoration apparatus 20 will be described. FIG. 4 is a process flow diagram showing the operation of the information restoration apparatus 20 according to the present embodiment.

  First, in S20, the feature acquisition unit 22 extracts a fiber pattern from the paper on which the digital watermark embedded document image is printed. Note that the document image is captured by the input unit 21 such as the scanner 104.

  Subsequently, the key generation unit 23 encodes the fiber pattern of the paper taken out by the feature acquisition unit 22, and generates a key stream (S21). Next, the information acquisition unit 24 extracts confidential information from the digital watermark embedded document image (S22). Next, the confidential information extracted by the information acquisition unit 24 is decrypted by using the key stream generated by the key generation unit 23 (S23). Then, error correction is performed on the decrypted confidential information (S24).

  Here, a specific process for extracting confidential information from a digital watermark embedded document image will be described.

  Using the extraction method for the embedding method described in S14 of FIG. 3, confidential information is extracted from the digital watermark embedded document image. Specifically, when embedding is performed by changing the dots that make up the character font that makes up the document image, the confidential information is determined by determining whether there is a change in the dots compared to the character font teacher data. To get. Also, in the case of embedding by changing the position of the characters that make up the document image, confidential information is acquired from the standard character position information by determining the displacement. Furthermore, in the case of embedding by drawing a pattern on the background of the document image, the pattern is recognized, and confidential information is acquired from a sequence of codes corresponding to the pattern.

  As described above, according to the information embedding device 10 and the information restoring device 20 shown in FIG. 2, unauthorized copying of confidential information can be prevented. That is, as shown in FIG. 8, when the paper on which confidential information is extracted is the same as the paper on which the confidential information is embedded, that is, the original, a key stream is generated from the fiber pattern of the same paper. Therefore, it is possible to extract confidential information. However, as shown in FIG. 9, when the paper from which the confidential information is extracted is not the same as the paper in which the confidential information is embedded, that is, a duplicate or a counterfeit, Since the stream is generated, the key stream itself is different and it is impossible to extract confidential information. Thus, since confidential information can be extracted only from the original, unauthorized extraction of confidential information can be prevented.

  Therefore, the information embedding device 10 and the information restoring device 20 can be applied to a system that protects the copyright of a paper from which information can be extracted only from the original. Furthermore, if the user does not know that the fiber pattern is used as a key, information cannot be extracted from the original, so that it can be used as steganography.

  In addition, as a specific process in the case where the paper from which the confidential information is extracted shown in FIG. 9 is not the same as the paper in which the confidential information is embedded, in addition to hiding the confidential information, for example, A process of notifying the user of a warning such as “This paper is a copy or a counterfeit” can be mentioned.

[Embodiment 2]
The second embodiment will be described below with reference to the drawings. FIG. 10 is a block diagram showing a schematic configuration of the information embedding device and the information restoring device according to the present embodiment. The difference from the first embodiment described above is that a two-dimensional coding unit (image coding means) 31 is added to the information embedding device 10 and that the information embedding unit 16 is a two-dimensional code adding unit (information (Embedding means) 32.

  The two-dimensional encoding unit 31 converts the confidential information encrypted by the encryption unit into a two-dimensional code. A specific example of the two-dimensional code includes a QR code.

  The two-dimensional code adding unit 32 functions as an information embedding unit. Specifically, the two-dimensional code adding unit 32 adds the two-dimensional code generated by the two-dimensional encoding unit to the printed matter.

  Since other components are the same as those in the first embodiment, detailed description thereof is omitted.

  The processing in the information embedding device 30 according to the present embodiment is realized by software executed on a CPU (Central Processing Unit) such as a computer or a workstation. In addition, in a copier having a printer or a printer function and a scanner function, it may be realized by software executed on a CPU that performs image processing and control, or may be realized as dedicated hardware.

(About information embedding device)
An operation of embedding information in the information embedding device 30 will be described. FIG. 11 is a processing flowchart showing the operation of the information embedding device 30 according to the present embodiment. It is assumed that the document image and confidential information are stored in advance in the memory 106, the fixed disk 107, and the like.

  First, in step (hereinafter abbreviated as S) 30, the document image and confidential information stored in the memory 106 or the fixed disk 107 are read by the information reading unit 11, and the paper fiber is read by the feature acquisition unit 13. The pattern is taken out.

  Subsequently, the key generation unit 14 codes the fiber pattern of the paper taken out by the feature acquisition unit 13 to generate a key stream (S31). Next, the coding unit 12 performs error correction coding on the confidential information read by the information reading unit 11 (S32). Next, the encryption unit 15 encrypts the confidential information that has been error correction encoded by the encoding unit 12 with the key stream generated by 14 in the key generation unit (S33).

  Next, the confidential information encrypted by the encryption unit 15 is two-dimensionally encoded by the two-dimensional encoding unit 31 (S34). Then, the confidential information that has been two-dimensionally encoded by the two-dimensional encoding unit 31 is added to the document image by the two-dimensional code adding unit 32 (S35).

  Note that the document image to which the confidential information is added is printed and output by the output unit 17.

  Here, the fiber pattern of the paper taken out by the feature acquisition unit 13 is taken out from an arbitrary position and an arbitrary range of the paper as in the first embodiment. The extraction position and range may be two-dimensionally encoded (image encoded) and added to the document image or embedded as a digital watermark. The taken-out fiber pattern of the paper is stored in the memory 106 or the fixed disk 107 by an existing image storage method such as bitmap or JPEG (Joint Photographic Experts Groups).

  A method for generating a key stream by encoding a fiber pattern is the same as that in the first embodiment. That is, as shown in FIG. 5, preprocessing such as density conversion processing and sharpening filter processing is performed on the fiber pattern, and feature amounts are extracted from the preprocessed image. Then, the extracted feature quantity is coded, and the coded code is used as a key stream. When the code is used as the key stream, the code stream may be repeated several times. The pre-processing and the feature amount acquisition method are not limited.

  Further, the process for error-correcting and encoding the confidential information and the process for encrypting the error-corrected encoded confidential information with the key stream are the same as in the first embodiment. That is, as shown in FIG. 6, the confidential information read from the memory 106 or the fixed disk 107 by the information reading unit 11 is subjected to error correction coding by the encoding unit, and the confidential information that has been encoded by the encryption unit 15 by the error correction coding. The information is encrypted using the key stream generated by the key generation unit 14. As a result, encrypted confidential information is obtained. The error correction coding uses existing techniques such as CRC (Cyclic Redundancy Checking) coding, BCH (Bose, Chaudhuri, Hocquenghem) coding, and RS (Reed Solomon) coding. Also, encryption using a key stream can be realized by performing confidential information and XOR (exclusive or) processing using a stream encryption (RC4 or the like) method.

  Here, FIG. 13 is a diagram showing a state in which the encrypted confidential information is two-dimensionally encoded. When the confidential information encrypted by the encryption unit 15 is two-dimensionally encoded, an error may occur when the two-dimensional code is read in the next process. It is preferable that the classified confidential information is repeatedly encoded a plurality of times. The above-described existing technique can be used for the error correction coding method.

  FIG. 14 is a diagram showing processing for adding a two-dimensional code to a document image. The position where the two-dimensional code is added may be an arbitrary position, but the size of the two-dimensional code needs to be determined according to the required accuracy of the scanner to be read. If the required accuracy is low, the two-dimensional code is enlarged, and if the required accuracy is high, the two-dimensional code is reduced and superimposed on the document image.

(About information restoration device)
As in the first embodiment, the information restoration device 20 is a device that takes in a document printed on a paper medium as an image and restores the information embedded by the information embedding device 30. The paper medium is printed by the information embedding device 30, and confidential information that is image-coded is added to the document image printed on the paper medium. In the following description, the document image is referred to as an image code-added document image.

  An operation of restoring the image code-added document image in the information restoration apparatus 20 will be described. FIG. 12 is a process flow diagram showing the operation of the information restoration apparatus 20 according to the present embodiment.

  First, in S40, the feature acquisition unit 22 extracts the fiber pattern from the paper on which the two-dimensional code and image code-added document image is printed.

  Subsequently, the key generation unit 23 encodes the fiber pattern of the paper taken out by the feature acquisition unit 22 to generate a key stream (S41). Next, the information acquisition unit 24 extracts confidential information from the image code-added document image (S42). Next, the secret information extracted by the information acquisition unit 24 is decrypted using the key stream generated by the key generation unit 23 (S43). Then, error correction of the decrypted confidential information is performed (S44).

  Here, the process of extracting the fiber pattern from the image code-added document image is the same as that in the first embodiment. That is, the position and range where the feature acquisition unit 22 extracts the fiber pattern of the paper are the same as the position and range where the feature acquisition unit 13 of the information embedding device 30 extracts. Here, as a configuration in which the feature acquisition unit 22 of the information restoration device 20 and the feature acquisition unit 13 of the information embedding device 30 take out the fiber pattern at the same position and range on the paper, the feature acquisition unit 13 takes out the fiber pattern. In addition, there is a method in which the range is previously two-dimensionally encoded and added to the document image, and the position and range where the fiber pattern is taken out are determined based on the added information. In addition, the information restoration device 20 and the information embedding device 30 share the same feature acquisition unit, and the information restoration device 20 uses the information (paper fiber pattern) extracted by the information embedding device stored in the feature acquisition unit. It is good also as a structure read from a feature acquisition part.

  Further, the process of coding the fiber pattern and generating the key stream is the same as the method performed by the key generation unit 23 in the information embedding device described above. Note that the information restoration device 20 and the information embedding device 30 may share the same key generation unit.

  Here, specific processing for extracting confidential information from the image code-added document image will be described.

  Using the extraction method for the embedding method described in S34 in FIG. 11, confidential information is extracted from the image code-added document image. Specifically, first, the information acquisition unit 24 takes in a two-dimensional code from an arbitrary position of an image code-added document image to which a two-dimensional code is added. Next, confidential information is extracted from the two-dimensional code by using the decoding method corresponding to the two-dimensional encoding method described in S34 of FIG. If an error correction code is used when the two-dimensional code is encoded, error correction is performed. Existing techniques can be used for error correction.

  The process of decrypting the confidential information using the key stream generated by the key generation unit 23 is the same as that in the first embodiment. That is, the decryption of confidential information can be realized by performing XOR processing with the confidential information. The error correction processing in S44 can use existing techniques such as CRC (Cyclic Redundancy Checking) coding, BCH (Bose, Chaudhuri, Hocquenghem) coding, and RS (Reed Solomon) decoding.

  As described above, according to the information embedding device 30 and the information restoration device 20 shown in FIG. 10, unauthorized copying of confidential information can be prevented. That is, as shown in FIG. 15, when the paper on which the confidential information is extracted is the same as the paper on which the confidential information is embedded, that is, the original, the key stream is generated from the fiber pattern of the same paper. , Confidential information can be extracted. However, as shown in FIG. 16, when the paper from which the confidential information is extracted is not the same as the paper in which the confidential information is embedded, that is, a duplicate or a counterfeit, Since the stream is generated, the key stream itself is different and it is impossible to extract confidential information. Therefore, fraudulent acts on confidential information can be prevented. In addition, it can be applied to a system for protecting the copyright of paper from which information can be extracted only from the original. Furthermore, if the user does not know that the fiber pattern is used as a key, information cannot be extracted from the original, so that it can be used as steganography.

  In this embodiment, since the two-dimensional code generated by the two-dimensional encoding unit 31 is added to the document image, the reading accuracy and processing speed can be improved as compared with the digital watermark method.

  The image code by the image encoding means is not limited to a two-dimensional code such as a QR code, but may be another image code, for example, a one-dimensional code such as a barcode.

  As described above, in each of the above embodiments, the information embedding device 10 (30) and the information restoration device 20 are configured by the same computer 100, and the feature acquisition unit 13 of the information embedding device 10 (30) and the information restoration device 20 The feature acquisition unit 22, the key generation unit 14 of the information embedding device 10 (30), and the key generation unit 23 of the information restoration device 20 may each be composed of the same components in the computer 100. As another configuration, the information embedding device 10 (30) and the information restoring device 20 may be configured by different computers.

  Here, the information embedding device includes an encryption unit for encrypting information to be embedded in the information embedding device for embedding information in the printed matter, and the key used for the encryption is based on the physical characteristics of the printed matter. It may be generated.

  The encryption unit may be configured to encrypt the information to be embedded after error correction encoding.

  Further, the physical characteristics may be a fiber pattern of paper constituting the printed matter.

The information to be embedded may be embedded in the document image as watermark information. The watermark information may be repeatedly embedded in an arbitrary range of the document image.

  Further, the watermark information may be repeatedly embedded in a part or the entire surface of the document image.

  Further, the information to be embedded may be added to the printed material as an image code.

  Moreover, the structure which the said image code produces | generates from the code | symbol which repeated the said information to embed may be sufficient.

  The information embedding method includes an encryption step for encrypting information to be embedded in the information embedding method for embedding information in a printed material, and the key used for the encryption is based on the physical characteristics of the printed material. It may be generated.

  The information embedding method may be executed by a computer.

  An image processing program for causing a computer to execute the information embedding method may be recorded on a machine-readable recording medium.

  Further, the printed matter may be a print of an image processed by the information embedding method.

  Finally, each block of the information embedding devices 10 and 30 and the information restoration device 20, in particular, feature acquisition units 13 and 22, key generation units 14 and 23, encryption unit 15, information embedding unit 16, information acquisition unit 24, decryption The unit 25 and the two-dimensional encoding unit 31 may be configured by hardware logic, or may be realized by software using a CPU as follows.

  That is, the information embedding devices 10 and 30 and the information restoration device 20 develop a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and the program. A random access memory (RAM), and a storage device (recording medium) such as a memory for storing the program and various data. An object of the present invention is to provide a recording medium on which a program code (execution format program, intermediate code program, source program) of an information embedding device control program, which is software that realizes the functions described above, is recorded in a computer-readable manner. This can also be achieved by supplying the information embedding apparatuses 10 and 30 and the information restoring apparatus 20 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  The information embedding devices 10 and 30 and the information restoration device 20 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be applied to a system that protects the copyright of paper from which information can be extracted only from the original.

1 is a block diagram illustrating a schematic configuration of a computer that functions as an information embedding device and an information restoration device according to an embodiment of the present invention. 1 is a block diagram showing a schematic configuration of an information embedding device and an information restoration device according to a first embodiment. FIG. 3 is a processing flowchart showing an operation example of the information embedding device shown in FIG. 2. FIG. 3 is a process flow diagram illustrating an operation example of the information restoration apparatus illustrated in FIG. 2. FIG. 3 is a diagram illustrating processing for generating a key from a fiber pattern of paper in the information restoration apparatus illustrated in FIG. 2. It is a figure which shows the process which encrypts using the produced | generated key in the information decompression | restoration apparatus shown in FIG. FIG. 3 is a diagram showing processing for embedding encrypted confidential information in a document image in the information restoration apparatus shown in FIG. 2. FIG. 3 is a diagram illustrating processing when the paper from which confidential information is extracted is the same as the paper in which confidential information is embedded in the information restoration apparatus illustrated in FIG. 2. FIG. 4 is a diagram illustrating processing when the paper from which confidential information is extracted is not the same as the paper in which confidential information is embedded in the information restoration apparatus illustrated in FIG. 2. It is a block diagram which shows schematic structure of the information embedding apparatus and information restoration apparatus which concern on 2nd Embodiment. FIG. 11 is a process flow diagram illustrating an operation example of the information embedding device illustrated in FIG. 10. It is a processing flowchart which shows the operation example of the information decompression | restoration apparatus shown in FIG. It is a figure which shows the state which carried out the two-dimensional encoding of the confidential information encrypted in the information embedding apparatus shown in FIG. It is a figure which shows the process which adds a two-dimensional code to a document image in the information embedding apparatus shown in FIG. FIG. 11 is a diagram illustrating processing when the paper from which confidential information is extracted is the same as the paper in which confidential information is embedded in the information restoration apparatus illustrated in FIG. 10. FIG. 11 is a diagram illustrating processing when the paper from which confidential information is extracted is not the same as the paper on which confidential information is embedded in the information restoration apparatus illustrated in FIG. 10.

Explanation of symbols

10, 30 Information embedding device 12 Encoding unit (encoding means)
13 Feature acquisition unit (Feature acquisition means)
14 Key generation part (key generation means)
15 Encryption section (encryption means)
16 Information embedding part (information embedding means)
20 Information Restoration Device 22 Feature Acquisition Unit (Feature Acquisition Unit)
23 Key generation part (key generation means)
24 Information acquisition unit (information acquisition means)
25 Decoding unit (decoding means)
31 Two-dimensional coding unit (image coding means)
32 Two-dimensional code adding part (information embedding means)

Claims (16)

In an information embedding device that embeds information in a printed matter,
Characteristic acquisition means for extracting physical characteristics of the printed matter;
Key generation means for generating a key associated with the printed material based on the physical characteristics of the printed material taken out by the feature acquisition means;
Encryption means for encrypting information embedded in the printed matter using the key generated by the key generation means;
An information embedding apparatus, comprising: information embedding means for embedding information encrypted by the encryption means in the printed matter. It further comprises encoding means for performing error correction encoding on information embedded in the printed matter,
The information embedding apparatus according to claim 1, wherein the encryption unit encrypts the information error-encoded by the encoding unit. The printed matter is paper,
The information embedding apparatus according to claim 1, wherein the physical characteristic of the printed matter is a fiber pattern of the paper.   The information embedding device according to claim 1, wherein the information embedding unit embeds the information in a printed matter by a digital watermark technique.   The information embedding apparatus according to claim 4, wherein the information embedding unit repeatedly performs the process of embedding the watermark information at an arbitrary position of the printed matter.   The information embedding apparatus according to claim 4, wherein the information embedding unit repeatedly performs the process of embedding the information in a part or the entire surface of the printed matter. Further comprising image encoding means for image-encoding the information encrypted by the encryption means,
4. The information embedding apparatus according to claim 1, wherein the information embedding unit adds the image code generated by the image encoding unit to the printed matter.   8. The information embedding apparatus according to claim 7, wherein the image encoding unit performs error correction encoding on the information encrypted by the encryption unit a plurality of times to generate an image code. An information restoration device for restoring information embedded in a printed material,
Characteristic acquisition means for extracting physical characteristics of the printed matter;
Key generation means for generating a key associated with the printed material based on the physical characteristics of the printed material taken out by the feature acquisition means;
Information acquisition means for extracting information embedded in the printed matter, encrypted using a key generated based on physical characteristics of the printed matter;
An information restoration apparatus comprising: a decryption unit that decrypts the information extracted by the information acquisition unit using the key generated by the key generation unit. The printed matter is paper,
The information restoration apparatus according to claim 9, wherein the physical feature of the printed matter is a fiber pattern of the paper. In an information embedding method for embedding information in a printed matter,
A feature acquisition step of extracting physical features of the printed matter;
A key generation step of generating a key associated with the printed material based on the physical characteristics of the printed material taken out by the feature acquisition step;
An encryption step for encrypting information to be embedded in the printed matter using the key generated by the key generation step;
An information embedding method comprising: an information embedding step of embedding the information encrypted by the encryption step in the printed matter. An information restoration method for restoring information embedded in a printed material,
A feature acquisition step of extracting physical features of the printed matter;
A key generation step of generating a key associated with the printed material based on the physical characteristics of the printed material taken out by the feature acquisition step;
An information acquisition step of extracting information embedded in the printed matter, encrypted using a key generated based on physical characteristics of the printed matter;
And a decrypting step of decrypting the information extracted by the information acquiring step using the key generated by the key generating step.   A control program for operating the information embedding device according to any one of claims 1 to 8, wherein the information embedding device control program causes a computer to function as each of the above means.   11. A control program for operating the information restoration apparatus according to claim 9 or 10, wherein the information restoration apparatus control program causes a computer to function as each of the above means.   A computer-readable recording medium on which the information embedding device control program according to claim 13 or the information restoration device control program according to claim 14 is recorded.   A printed matter in which information is embedded by the information embedding method according to claim 11.

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